The present invention relates to a phased array antenna apparatus which electronically changes a phase fed to a plurality of radiation elements to scan a radiation beam.
A phased array antenna apparatus of this type radiates an electromagnetic wave as a radiation beam in a desired direction and therefore is fixed on the ground or mounted on a movable body and used for satellite communication or satellite broadcasting reception.
In the phased array antenna apparatus, power for driving the radiation elements is supplied from a power supply unit and distributed and fed to the radiation elements by a power distributor. A phase shifter is connected between the power distributor and each radiation element. The phase to be fed to each radiation element is changed by controlling the phase shifter.
Each radiation element radiates a wave with a phase corresponding to the fed phase. Therefore, when the phase shifters are controlled such that an equiphase plane is generated by radiation from the radiation elements, a radiation beam can be formed in a direction perpendicular to the equiphase plane.
The conventional power distributor is constituted by a microstrip line for connecting the phase shifter arranged for each radiation element to the power supply unit. However, the microstrip line has a large loss in a high-frequency band. Since the microstrip line is an open line, the radiation loss increases as the frequency rises. In addition, since the high-frequency current flows only through the surface layer due to the skin effect, the transmission loss increases.
As described above, when the conventional phased array antenna apparatus is used in a high-frequency band, the feed loss in the power distributor increases.
It is an object of the present invention to provide a phased array antenna apparatus which reduces the feed loss in a high-frequency band.
In order to achieve the above object, according to the present invention, there is provided a phased array antenna apparatus comprising a plurality of radiation elements aligned and arranged to be electromagnetically driven, power supply means for supplying power to the radiation elements, power distribution means for distributing the power supplied from the power supply means to the radiation elements, the power distribution means having a pair of conductive plates arranged to be parallel to each other and constituting a radial waveguide, a feed probe arranged on one of the conductive plates to radiate an electromagnetic wave into the radial waveguide in accordance with the power supplied from the power supply means, a plurality of electromagnetic coupling means, arranged on the other of the conductive plates in correspondence with the radiation elements, for extracting the electromagnetic wave radiated from the feed probe and propagating through the radial waveguide by electromagnetic coupling, and a plurality of phase control means for controlling a phase of the electromagnetic wave extracted by the electromagnetic coupling means and supplying the electromagnetic wave to the radiation elements.